We present new biostratigraphic results from two ophiolite outcrops in Armenia. The discovery of upper Tithonian–lower Berriasian diagnostic radiolarian species (Vallupus gracilis Li and Sashida) in the lower radiolarites of the Dali section allows to date more accurately submarine lava eruptions of transitional to alkaline composition. The radiolarian results also indicate that blocks of shallow-water carbonates slid into the basin during this time interval. At Vedi, upper Coniacian–Santonian calcareous nannofossils identified in marls of the post-obduction sedimentary cover refine previous age data. Synthesis of the existing bio-chronostratigraphic constraints in Armenia and Karabagh sheds light to the depositional and magmatic history of Tethys in the Lesser Caucasus and highlights the age constraints of fossils on the timing of ophiolite obduction in the region.

High-resolution structural analysis of stratigraphically-controlled units within North Dobrogea (ND), based on fieldwork and the production of new cross-sections as well as a reconstruction of the Mesozoic paleo-stress regimes, has resulted in a revision of the tectonic events across the region as well as demonstrating the significance of tectonic inheritance. The observed structures are closely related to the major strike-slip faults of the Teisseyre-Tornquist Zone (TTZ) a lithospheric structure active during the early and middle Mesozoic. The significance of this zone has been underestimated in previous kinematic reconstructions examining the opening of the continental back-arc basin of the Black Sea. Integrating the present results with existing knowledge on the tectonic evolution of the Black Sea, suggests a new conceptual kinematic model for further testing, one that involves movement of the continental fragment of Moesia NW along the TTZ during the early and middle Mesozoic. Such a displacement would represent the westernmost occurrence of the Cimmerian orogeny in the region of the western Black Sea. The escape of Moesia to the NW could possibly explain the polyphase extension of the western Black Sea crust, which developed on the continental Eurasian Plate as a back-arc basin due to the N-directed subduction of Tethys.

This paper presents a chronology of tectonic events in the Crimean Mountains (CM) based on a micro- (palaeostress) and macro-scale (tectonic structures) structural analysis since the Cretaceous. Recent studies have attempted to fit the geology of the CM into the geodynamic context of the subduction of the Neotethys plate beneath the Eurasian margin; however, these attempts remain difficult and controversial as they are based dominantly on stratigraphic analysis. New structural analysis results indicate that structural development within the CM was largely determined by the influence of pre-existing structures that occurred long before the Cretaceous rifting in the Black Sea (BS). This could explain the features of the geological structure in the Western and Eastern CM separated by the Alushta-Simferopol Fault Zone (ASFZ). New palaeo-stress analysis allows us to identify the trends and timing of the Mesozoic-Cenozoic tectonic deformations with greater precision. Superimposing the low-magnitude seismicity (M <= 3) with structures defined on the established geological crosssections permit the localization of currently active structures. Considering both recent scientific achievements concerning the geology of the CM and the results of this study, we propose a qualitative model of the formation of the BS Basin and its inversion in the context of the BS-Greater Caucasus (GC). In this model, the Shatsky Ridge (ShR), moving to the north, acts as an indenter deforming the CM and the GC. The results are of practical importance for geodynamic modelling and hydrocarbon exploration.

We present new, geological, metamorphic, geochemical and geochronological data on the East Anatolian-Lesser Caucasus ophiolites. These data are used in combination with a synthesis of previous data and numerical modelling to unravel the tectonic emplacement of ophiolites in this region. All these data allow the reconstruction of a large obducted ophiolite nappe, thrusted for >100 km and up to 250 km on the Anatolian-Armenian block. The ophiolite petrology shows three distinct magmatic series, highlighted by new isotopic and trace element data: (1) The main Early Jurassic Tholeiites (ophiolite s.s.) bear LILE-enriched, subduction-modified, MORB chemical composition. Geology and petrology of the Tholeiite series substantiates a slow-spreading oceanic environment in a time spanning from the Late Triassic to the Middle-Late Jurassic. Serpentinites, gabbros and plagiogranites were exhumed by normal faults, and covered by radiolarites, while minor volumes of pillow-lava flows infilled the rift grabens. Tendency towards a subduction-modified geochemical signature suggests emplacement in a marginal basin above a subduction zone. (2) Late Early Cretaceous alkaline lavas conformably emplaced on top of the ophiolite. They have an OIB affinity. These lavas are featured by large pillow lavas interbedded a carbonate matrix. They show evidence for a large-scale OIB plume activity, which occurred prior to ophiolite obduction. (3) Early-Late Cretaceous calc-alkaline lavas and dykes. These magmatic rocks are found on top of the obducted nappe, above the post-obduction erosion level. This series shows similar Sr-Nd isotopic features as the Alkaline series, though having a clear supra-subduction affinity. They are thus interpreted to be the remelting product of a mantle previously contaminated by the OIB plume. Correlation of data from the Lesser Caucasus to western Anatolia shows a progression from back-arc to arc and fore-arc, which highlight a dissymmetry in the obducted oceanic lithosphere from East to West. The metamorphic P-T-t paths of the obduction sole lithologies define a southward propagation of the ophiolite: (1) P-T-t data from the northern Sevan-Akera suture zone (Armenia) highlight the presence and exhumation of eclogites (1.85 +/- 0.02 GPa and 590 +/- 5 degrees C) and blueschists below the ophiolite, which are dated at ca. 94 Ma by Ar-Ar on phengite. (2) Neighbouring Amasia (Armenia) garnet amphibolites indicate metamorphic peak conditions of 0.65 +/- 0.05 GPa and 600 +/- 20 degrees C with a U-Pb on rutile age of 90.2 +/- 5.2 Ma and Ar-Ar on amphibole and phengite ages of 90.8 +/- 3.0 Ma and 90.8 +/- 1.2 Ma, respectively. These data are consistent with palaeontological dating of sediment deposits directly under (Cenomanian, i.e. >= 93.9 Ma) or sealing (Coniacian-Santonian, i.e., <= 89.8 Ma), the obduction. (3) At Him (NE Turkey) P-T-t conditions on amphibolites (0.66 +/- 0.06 GPa and 660 +/- 20 degrees C, with a U-Pb titanite age of 80.0 +/- 3.2 Ma) agree with previous P-T-t data on granulites, and highlight a rapid exhumation below a top-to-the-North detachment sealed by the Early Maastrichtian unconformity (ca. 70.6 Ma). Amphibolites are cross-cut by monzonites dated by U-Pb on titanite at 78.3 +/- 3.7 Ma. We propose that the HT-MP metamorphism was coeval with the monzonites, about 10 Ma after the obduction, and was triggered by the onset of subduction South of the Anatolides and by reactivation or acceleration of the subduction below the Pontides-Eurasian margin. Numerical modelling accounts for the obduction of an "old" similar to 80 Myr oceanic lithosphere due to a significant heating of oceanic lithosphere through mantle upwelling, which increased the oceanic lithosphere buoyancy. The long-distance transport of a currently thin section of ophiolites (<1 km) onto the Anatolian continental margin is ascribed to a combination of northward mantle extensional thinning of the obducted oceanic lithosphere by the Hinis detachment at ca. 80 Ma, and southward gravitational propagation of the ophiolite nappe onto its foreland basin. (C) 2019, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.

The Paleocene-Miocene Ararat basin is located in the foreland to the south of the NW-SE trending Lesser Caucasus orogenic belt in the Republic of Armenia.In the foreland to the north are the hydrocarbon-bearing Kura andRioni basins of Georgia. On the basis of recent studies in Armenia together with a critical review of previous work, we propose a new model for the structure and development of the Ararat basin. The basin's development is here interpreted within a compressional regional framework which has been dominated since the Late Cretaceous by the closure of Neotethys and the Arabia-Eurasia collision. Previous studies have considered that the Ararat basin is an extensional graben, and that surface exposures of Palaeozoicrocks are related to horst structures controlled by normal faults. However new data suggest that surface structures in a study area in the northern flank of the basin arein fact oblique-slip reverse and thrust faults, activated in post-Oligocene-Miocene times (Fig.1). Regional compression resulted in the formation of asymmetric, fault-controlled folds including the Lanjanist and Urts anticlines to the NW of the Ararat basin and Parakar-bared and Sardarapat structures to the north and NW. The structural pattern is complicated by secondary normal faults which have resulted in gravitational slope processes and erosion. Pliocene and Quaternary (active) structures show evidence of structural inheritance. In the subsurface, the Ararat basinis interpreted to contain obduction-related ophiolitic nappes which are exposed at the surface at various locations such as Sari Pap. Together with compressional anticlines and thrust faults, these Mesozoic nappes have potential as structural traps for hydrocarbons.

The Sevan-Akera suture zone ophiolites are relics of a vast ophiolitic nappe which testifies a major obduction event, up to 300 km of horizontal transport, of the northern branch of Neotethys oceanic crust over the South Armenian/Taurides continental block. Near the locality of Amasia (NW Armenia), garnet-bearing amphibolites are preserved within a greenschist facies tectonic melange unit located below the non-metamorphic obducted oceanic unit. The garnet amphibolites show two parageneses: (1) garnet-amphibole-plagioclase granoblasts which crystallized along the S-1 foliation intensely folded and recrystallized into (2) epidote-chlorite-phengite during retrogression and S-2 deformation. S-1 and S-2 deformation stages feature top-to-the-South ductile shearing, interpreted as the motion of the ophiolite nappe during obduction. Thermobarometry reveals a metamorphic history with two P-T fields: (1) an amphibolite stage, T = 600 +/- 20 degrees C and 6 <= P <= 7 kbar, followed by (2) a greenschist stage, T = 350 +/- 30 degrees C and 1.25 <= P <= 4.5 kbar. Ar-40/Ar-39 dating on amphiboles and white micas yields similar within-error ages of 88-92 +/- 2 Ma. U-Pb dating on rutile yields an age of 90.2 +/- 5.2 Ma. These results are complemented by new and pre-existing characterizations of lithologies in a similar structural position 40 km east, in the locality of Stepanavan. There, newly identified eclogite yield metamorphic conditions of T = 575 +/- 25 degrees C and 17.5 <= P <= 20 kbar. The P-T-t history of these metamorphic units argues for a rapid tectonic process featuring intra-oceanic subduction below a relatively hot oceanic lithosphere, slicing of the overriding oceanic domain, underplating of this subducted material along the hanging wall of the subduction zone and formation of a metamorphic sole as part of an 'obduction channel'.

The current work is focused on our main results concerning the tectonic evolution of the Black Sea-Greater Caucasus domain obtained during decades of detailed studies in the framework of DARIUS programme and GDRI South Caucasus Geosciences project of the CNRS/INSU. Results of this analytical work allowed us to establish a paleo-reconstruction of the whole of the southern margin of the European craton, during much of the Phanerozoic (Barrier E et al in Paleotectonic reconstruction of the Central Tethyan Realm. CCGM/CGMW, Paris, 2018 [3]). Focusing on Black Sea-Greater Caucasus domain we present a state of the art about analysis of this area, highlighting the perspectives of new investigations at question not solved by the tectonic and geodynamic evolution of these basins.

This paper investigates the structure of the northern margin of the Ararat depression in a study area in SE Armenia. The depression is a Cenozoic intermontane basin located to the south of the Lesser Caucasus. The purpose is to improve understanding of the basin's structure and origin within a regional tectonic framework which has been dominated since the Late Cretaceous by the closure of Neotethys and the Arabia-Eurasia collision. We suggest that the depression is not a graben controlled by normal faults; rather, based on detailed observations, structures in the study area are interpreted as oblique-slip reverse and thrust faults activated in post Oligocene-Miocene times. These compressional faults resulted in the formation of asymmetric fold structures including the Lanjanist and Urts anticlines which are well expressed in the surface relief to the north of the Ararat depression. In general the structural pattern is complicated by secondary normal faults which resulted in superimposed gravitational slope processes and erosion. Major structures in the study area originated in a compressional setting associated with the closure of Neotethys since the latest Cretaceous. Post-collisional strike-slip faulting was linked to convergence of the Arabian and Eurasian plate margins. Pliocene and Quaternary structures, some still active, show evidence of structural inheritance. The Armenian portion of the Ararat depression contains obduction-related nappes, anticlines and thrust faults which have potential as structural traps for hydrocarbons. These should be investigated in detail using advanced geophysical methods including 2D and 3D seismic analyses.

The work poses the question about the impact of inherited structures in the Black Sea back-arc basin (BAB) tectonic evolution. The new structural analysis of the Northern Dobrogea (ND) and the Crimean Mountains (CM) shows that the origins of structural patterns of both regions are in close relationship with deep faults/or fault zones. The comparative analyses of structures, of tectonic stages and their duration allow us to better understand the connections in time and space between the ND and the CM, against the back-ground of the long-living subduction. In particular during: (1) the Cimmerian orogeny; (2) the opening of the BS and (3) the inversion of the BS during the Cenozoic shortening.

Micropalaeontological age evidence for the sedimentary cover of ophiolites is important to understand the palaeogeographic and geodynamic evolution of Tethyan realms. The Stepanavan ophiolitic suite of Northern Armenia consists of peridotites, gabbros, plagiogranite and lavas with a radiolarite sedimentary cover. It is regarded as the northern extension of the Sevan Akera ophiolitic zone and may be considered as the eastern extension of the Izmir-Ankara suture zone. It represents the relics of a slow-spreading mid oceanic ridge that was active between Eurasia and the South-Armenian Block of Gondwanian origin. Radiolaria extracted from radiolarites of the Stepanavan ophiolite provide for the first time a Late Jurassic (late Kimmeridgian to early Tithonian) age constraint for this part of Tethyan oceanic crust preserved in Lesser Caucasus.

This Special Publication presents the results of 15 different studies in the Black Sea-Caucasus segment of the Alpine-Tethys orogenic realm.The main focus of these studies is the style and timing of key tectonic events occurring primarily during the area's post-Pangaean evolution.The methodologies encompass: geophysics, including active and passive crustal-scale seismology and common depth point reflection seismic profiling (both onshore and marine), palaeomagnetism and magnetostratigraphy; field geology, including biostratigraphic recorrelation; radiochronology; igneous rock geochemistry, including analyses of the obducted ophiolites; and low-temperature thermochronology.The geological record of the area is essentially one of sedimentary basins formed in an extensional back-arc setting and their subsequent compressional deformation during the closure of at least two branches of the Neotethys Ocean system.

Our study focused on the structural geometry at the eastern Achara-Trialeti fold and thrust belt (ATFTB) located at the retro-wedge of the Lesser Caucasus orogen (Alania et al., 2016a). Our interpretation has integrated seismic reflection profiles, several oil-wells, and the surface geology data to reveal structural characteristics of the eastern ATFTB. Fault-related folding theories were used to seismic interpretation (Shaw et al., 2004). Seismic reflection data reveal the presence of basement structural wedge, south-vergent backthrust, north-vergent forethrust and some structural wedges (or duplex). The rocks are involved in the deformation range from Paleozoic basement rocks to Tertiary strata. Building of thick-skinned structures of eastern Achara-Trialeti was formed by basement wedges propagated from south to north along detachment horizons within the cover generating thin-skinned structures. The kinematic evolution of the south-vergent backthrust zone with respect to the northward propagating structural wedge (or duplexes). The main style of deformation within the backthrust belt is a series of fault-propagation folds. Frontal part of eastern ATFTB are represent by triangle zone (Alania et al., 2016b; Sosson et al., 2016). A detailed study was done for Tbilisi area: seismic refection profiles, serial balanced cross-sections, and earthquakes reveal the presence of an active blind thrust fault beneath Tbilisi. 2 & 3-D structural models show that 2002 Mw 4.5 Tbilisi earthquake related to a north-vergent blind thrust. Empirical relations between blind fault rupture area and magnitude suggest that these fault segments could generate earthquakes of Mw ∼ 6.5. The growth fault-propagation fold has been observed near Tbilisi in the frontal part of eastern ATFTB. Seismic reflection profile through Ormoiani syncline shows that south-vergent growth fault-propagation fold related to out-of-the-syncline thrust. The outcrop of fault-propagation fold shown the geometry of the hangingwall structure with the syn-folding growth stratal sequence. Pre-growth Oligocene strata are overlain by Late (?) Quaternary alluvial fan gravels, sands and clays. Growth unconformity of back-limb showing flat clays unconformably on top of Oligocene sandstone and shale beds. The growth strata geometry of growth fold is related to the progressive limb-rotation model (Hardy & Poblet, 1994).

Abstract The Khoy region (NW Iran) is important in the clarification of the structural framework of the alpine belt between the Taurides, the Lesser Caucasus and the NW Iran belt. The area is well-known for these ophiolitic units. We present here new stratigraphic and structural data that can be used to reconstruct the tectonic evolution of this region and then try to establish connections between these belts. According to new dates from nannoplankton assemblages, the obducted ophiolite of the Khoy complex was thrust over a sheared Campanian olistostrome and lenses of amphibolite are included within the contact. The obduction event is also marked by erosion of the ophiolitic unit and the deposition of conglomerates, shales, sandstones and siltstones. Poorly extended Paleocene detrital deposits cover the Campanian–Maastrichtian rocks. The Eocene formations characterize a basin filled with volcanogenic and sedimentary layers. The Middle and Upper Eocene series unconformably overlie the ophiolites and their cover of Campanian–Maastrichtian and Paleocene deposits. This corresponds to a syn-orogenic basin formed after the collision between Eurasia and the Taurides–Anatolides–South Armenian microplate. The Oligocene–Miocene Qom Formation with basal conglomerates unconformably covers all the earlier formations, including the Palaeozoic formations, indicating intense shortening before its deposition. Compressional deformation continued and is manifested by numerous folds, mainly west-dipping thrusts and reverse faults cutting the Qom Formation, and by recent NW–SE dextral strike-slip faults. This illustrates the continuous shortening and uplift (with intense erosion) resulting from the advanced stage of the collision between Arabia and Eurasia. The structural location of the tectonic units suggests that the Khoy Gondwana-related basement was part of the South Armenian Block and that the Khoy allochthonous ophiolites were obducted on it from the Amasia–Stepanavan–Sevan–Hakari suture zone.

We present arguments for an innovative tectonic set-up just prior to the Northern Neotethys obduction event in the NE Anatolian and Lesser Caucasus area. Along the Northern Neotethyan suture (the Ankara-Erzincan-Amasia-Sevan-Akera suture zone), relicts of the northern branch of the Neotethys oceanic domain outcrop as preserved unmetamorphosed slivers obducted over the northern edge of the South Armenian Block (SAB) and Taurides-Anatolides Platform (TAP) margins. Recent studies have shown that the ophiolitic bodies are formed of similar lithologies of Middle Jurassic age, all bearing mid-ocean ridge basalt chemical compositions enriched in large ion lithophile elements. This extensive database supports a model in which these ophiolites are derived from a single obducted nappe. This model is supported by the metamorphic pressure-temperature-time paths of the sole lithologies under the outcrops of the suture zone ophiolites. Palaeontological dating of sediment deposits directly under or sealing the obduction contact also support this model by temporally linking the emplacement of distant ophiolite outcrops. General emplacement during early Late Cretaceous time has been determined. A south-dipping subduction under the SAB shortly predating obduction has recently been proposed from the metamorphic and magmatic evolution preserved in the SAB crystalline basement, founding a model featuring opposite-direction subduction from at least late Middle Jurassic to Early Cretaceous times. The emplacement of alkaline pillow basalts directly on the oceanic crust is dated as Early to mid-Cretaceous. These dates argue the existence of abnormal mantle heat flows which may be responsible for a decrease in the density of the 80 Ma-old oceanic lithosphere prior to its obduction onto the SAB-TAP. We present a detailed review of recent data to further constrain the structural and geodynamic evolution of this sector and to define the tectonic set-up just prior to the obduction event.